This invention relates generally to a laser apparatus and more particularly to a compact laser construction instrument that is adapted to home-construction use.
It is known to provide a laser construction instrument that generates a rotating plane of laser light for surveying purpose as well as for guiding excavators, road graders and the like. Such instruments are capable of generating a laser plane that is accurate to 1/16 of an inch per 100 foot of distance. Such accuracy comes at a price and typically requires complex optical systems and a self-leveling mechanism. While the expense is justified for large scale construction usage, it becomes prohibitive for casual users, particularly for home builders and home owners. While it is known to utilize such a construction laser plane generator for laying out the grid of a suspended ceiling, the known laser plane generators are beyond the price point of all but the professional ceiling contractors.
The known laser plane generator generates a collimated beam of light in a vertical axis, which is deflected by a rotating deflection device into a horizontal plane that rotates using a rotating penta-prism or penta-reflector. It has been discovered that enhanced performance may be obtained by using a rotating penta-prism or penta-reflector that reflects only a portion of the vertical beam into the horizontal while providing a beam which passes through the penta-prism or penta-reflector in the vertical axis. This provides a beam of light that is perpendicular to the generated light plane. This can be used for setting walls and foundations and the like at true right angles. The difficulty with such known devices is that both the penta-prism and penta-reflector impose a lateral offset to the vertical axis beam, requiring compensation. If such compensation were not provided, a rotating cylinder, rather than a rotating beam, would be provided. Such compensation adds additional expense to an already costly device. The penta-prism and penta-reflectors are precision optic devices costing several hundreds of dollars a piece.